The invention relates to a device to detect individual moving objects having very small dimensions, particular dimensions in the sub-mm range.
Photo electric sensors are frequently used to detect moving objects. The measurement volumes of photo electric sensors without additional beam-forming optics that are available on the market are too large, that is, the diameter of the optical path is too large to detect very small individual objects with a high repeat rate and with short object spacing. Beam-forming optics that could remedy this problem need a large installation space compared to the very small objects. If there is only a restricted installation space available, these kinds of photo electric sensors cannot be employed.
Existing evaluation electronics analyze the changes in the signal when an object passes through and thus recognizes the objects. Particularly in the case of very small objects, however, environmental influences, electrical disturbances and transit phenomena result in faulty detection since the signal picked up by the light beam receiver is very small compared to the interfering signals. These kinds of evaluation circuits do not produce a counting result that is sufficiently reliable in order to count, for example, drops of liquid that have a diameter of 200 μm or less.